Answer:
Multiple alleles
Step-by-step explanation:
An example of multiple alleles is the ABO blood group system in humans. Human gene I (isohaemagglutinin) exists in three allelic forms: Iᴬ, Iᴮ, and i. Iᴬ and Iᴮ produce type A and type B whereas i which is a recessive allele does not produce antigen. Therefore, blood type exists as four possible phenotypes: A, B, AB, & O.